On Wed, Jun 18, 2014 at 2:26 PM, Judson <

[hidden email]> wrote:

> Dear Dr. Bates,

> I'm just learning R and I want to use it for

> statistical problems and also some problems

> that are just mathematical. Apparently I'm

> not using the packages right and none of the

> books I've found cover what should be simple

> operation, inverting a matrix. Can you point

> me in the right direction?

> ..................... judson blake

>

It is usually more effective to submit questions like this to the

[hidden email] mailing list which I am cc:ing on this reply. Many

people who read that list can respond and usually much faster than I do.

The short answer to your question is

solve(A)

> A <- matrix(rnorm(16),nc=4)> Ainv <- solve(A)> zapsmall(Ainv %*% A) [,1] [,2] [,3] [,4]

[1,] 1 0 0 0

[2,] 0 1 0 0

[3,] 0 0 1 0

[4,] 0 0 0 1

The longer answer to your question is that you may think you need to

calculate the inverse of a matrix but you probably don't. Inverses occur

frequently in formulas and much less frequently in actual computation that

has a chance of scaling well. In numerical linear algebra one factorizes a

matrix and works with the factors.

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